The invention relates to a method for layerwise production of a tangible object. The invention also relates to a system for layerwise production of a tangible object.
Such techniques are used in the field of Layered Manufacturing Technology (LMT), often referred to as Rapid Prototyping (RP) or Rapid Manufacturing (RM), to produce a tangible object. Rapid Prototyping (RP) and Rapid Manufacturing (RM), are called “rapid” since they do not require a mould to be designed and manufactured.
The solidifying can use any suitable chemical or physical process to solidify the predetermined area of the liquid layer. The solidifying means may for example initiate a chemical reaction of a component in the liquid which results in a solid reaction product. For example, the liquid may be a liquid resin which can be cured by electro-magnetic radiation, for example a photo-polymer of which polymerisation can be activated by projecting light of a suitable wavelength. The liquid can be transformed into a solid by a suitable type of energy and the solidifying means may include a source of energy which can selectively provide the energy to the predetermined area. The source of energy may for example include a source of electro-magnetic radiation. The solidifying means may include a light source which can emit light which is projected onto the predetermined area of the liquid layer via a projection unit of the solidifying means in a pattern corresponding to the desired shape and size of the solid layer.
Several techniques are known for creating a successive uppermost liquid layer of the liquid.
For example, it is known to apply a thicker than required layer of liquid by flooding the already built part of the object under construction. Then, the excess material is removed by means of a wiper blade. The wiping results in forces being transmitted to the object under construction. In order to avoid that these forces are becoming too high, the wiping has to be performed with restricted speed. In addition, such speed restriction is necessary in order to avoid that hollow spaces of the object under construction are being emptied by the action of the wiper blade.
In another known technique, a construction shape is applied, which construction shape is transparent for radiation incident from above. In each method cycle, the solidifying of the predetermined area of the liquid layer is carried out when said liquid layer is adjoining the construction shape. After solidifying, the obtained solid layer is separated from the construction shape. The separating results in forces being transmitted to the object under construction. In order to avoid that these forces are becoming too high, the separating has to be performed with restricted speed. Another factor that results in restricted speed of this known technique, is that it takes relatively long time for the liquid to flow in between the construction shape and the object under construction.
A further known technique is disclosed in WO97/29901. In this known technique a controllable means is provided above a vessel filled with a hardenable liquid medium. The controllable means contains a casting bob which is erected on top of the vessel and is provided with a slot at the bottom, and means to move said casting bob in a relative manner over the surface of the medium contained in the vessel. The liquid medium is cast, in the form of a stable curtain, on a previously formed layer. A drawback of this known technique is that, the thinner the new liquid layers are required to be, the more difficult (or even impossible) it is to produce these by means of such stable curtain. Hence, there is a limitation on the shallowness of the new layers to be created, which results in a limitation on the accuracy of the object to be produced.
It is furthermore remarked that U.S. Pat. No. 5,358,673A discloses a method as well as a system for layerwise production of a tangible object. For instance, the spraying is disclosed in column 2, line 47 of U.S. Pat. No. 5,358,673A.